System for Determining the Airspeed of an Aircraft

Abstract

A system for determining the true airspeed vector, defined by a magnitude and by a direction, of an aircraft comprising a fuselage, comprises four laser anemometers each having a single measurement path so as to measure a local component of the true airspeed and being distributed in different locations around the fuselage of the aircraft; and means for calculating the magnitude and direction of the true airspeed vector of the aircraft using the four measurements of components of the true airspeed.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority to foreign French patent application No. FR 1003994, filed on Oct. 8, 2010, the disclosure of which is incorporated by reference in its entirety.FIELD OF THE INVENTION[0002]The invention relates to the field of anemometer measurements onboard fixed-wing aircraft.BACKGROUND[0003]Onboard anemometer measurements notably aim to determine the following values located at infinity upstream: the true airspeed (or TAS), the angle of attack, the sideslip, the calibrated airspeed and the static pressure of the aircraft or the pressure altitude.[0004]It will be recalled that:[0005]the true airspeed V is the speed of an aircraft relative to undisturbed air;[0006]the angle of attack is the angle α formed between the velocity vector V of the aircraft and the longitudinal axis;[0007]the sideslip is the angle between the velocity vector V and the (vertical) plane of symmetry of the aircraft;[0008]the static pressure (Ps) is...

AI Technical Summary

Benefits of technology

[0042]The invention notably aims to alleviate the aforementioned problems by providing a system for determining the airspeed of an aircraft more reliably, the system also being easier to install on the fuselage of the aircraft.

[0043]The invention thus makes the measurement of airspeed parameters easier.

[0048]Laser anemometers have safety advantages (no risk of icing, dissimilarity to a conventional system, reliability and insensitivity to aerosols).

[0049]The invention makes it possible to avoid the use of fragile and protruding angle-of-attack probes and pitot tubes and probes. These devices, which are particularly sensitive to icing, are replaced by more resistant laser anemometers that do not protrude.

Problems solved by technology

These local measurements are carried out near the fuselage and are therefore subject to the disturbances generated by the latter.

These systems notably have the drawback of requiring measurement instruments, for example vanes, which are fragile, because they are light, and particularly sensitive to icing.

These systems are furthermore difficult to install because the measurement instruments must moreover be placed at specific points on the fuselage of the aircraft so as to minimize measurement errors related to disturbances.

However, such a system has the drawback of requiring a powerful laser with a wide aperture.

In addition, determining three appropriate measurement points can be difficult.

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